Radiation Pattern Diversity Research Articles

Rectangular Microstrip Antenna on Ridge Ground Plane to Control the Resonant Modes for Improved Bandwidth using Transverse Resonance Method

A single layer single element rectangular microstrip antenna on ridge ground plane for improved bandwidth is theoretically investigated with a view to develop a concrete physical insight in to the phenomenon. The simple single element probe fed rectangular microstrip antenna fabricated on conventional PTFE (Poly Tetra Fluride Ethelene) substrate have many advantages except its narrow bandwidth. The present study proposes the technique to control the resonant modes of a microstrip antenna for yielding better bandwidth using transverse resonance method. The present antenna is designed to fabricate on ridge ground plane which has been compared with conventional structure and around 6% - 7% improvement in bandwidth is revealed. The detailed variation of radiation pattern across its frequency band has been studied and presented in this paper. The proposed idea has been verified through a commercial software package (High Frequency Structure Simulator) for a patch operating in X band and explained quantitatively. The electric surface current distribution over the patch surface for both the conventional and proposed antenna is presented to explain the broad banding effect physically.

배열 안테나용 AEM형 FSS 레이돔 설계

In this paper, we present a design of AEM radome with frequency selective surface using unit-cell EM simulation method and verified the performance of AEM radome by the radiation pattern measurements of array-antenna. Measured results under near-field condition showed a good agreement with the simulation and far-field measured ones. And there were no radiation pattern variation between antenna only and antenna with AEM radome. From these results, we verified that AEM radome with frequency selective surface can be a solution to reduce the RCS of conventional mast and radar.

Compact hybrid CPW‐FED slot antenna array with pattern diversity

AbstractIn this paper, a compact hybrid coplanar waveguide (CPW) fed 1 × 2 slot antenna array with radiation pattern diversity is proposed for the wireless local area networks (WLAN) application.The antenna array consists of two rectangular slot radiation elements, two feed slots, a CPW and an open‐ended strip. The feed network provides out‐phase and in‐phase feed with high isolation in a relatively compact structure without any lossy circuits, and difference and sum radiation patterns are achieved in the azimuth plane with wide bandwidths of 480 MHz (20%) and 580 MHz (24.2%). The measured gains of dual‐pattern are better than 4.93 and 3.76 dBi in the WLAN band (2.4–2.484 GHz). The proposed dual‐port array can be used as pattern diversity in modern mobile system. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:884–888, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25879

Beam Scanning Array Using Spatial Diversity

In this work, an array antenna based on antenna spatial diversity is developed. The antenna system contains 16 elements arranged as a linear array. In operation, only four elements are activated via RF switches while others are disconnected. By changing the combination of activated elements, diverse radiation patterns are produced. Array factor patterns calculated from all possible combinations are searched to edit a switching sequence to maximize gains at desired directions. A scanning beam can be therefore synthesized. The beam scanning performance is verified via comparison of computed and measured radiation patterns. In order to minimize the gain differences during scanning, a linear array with non-uniform element spacing is proposed. Although the antenna array developed here is relatively large compared to conventional phased array, it is an attractive alternative because of features such as simple structure, low cost, and low insertion loss.

Millimetre‐wave polarization‐dependant monopulse printed Fresnel reflector

AbstractThis article describes the principle of combining circular or annular patches with C‐patches on a Fresnel reflector that introduces radiation pattern diversity according to the polarization. Patches were designed to perform a 180° phase difference of the reflection phase between two orthogonal polarizations for a monopulse antenna purpose. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 25–28, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24822

A Novel Pattern Diversity Reflector Antenna Using Reconfigurable Frequency Selective Reflectors

A radiation pattern diversity reflector antenna is investigated. Novel switchable frequency selective reflectors are designed and developed to construct a square corner reflector antenna. By controlling a switching device on the frequency selective reflector, one can make it opaque or transparent to a vertically polarized incident wave. This antenna is fed by a monopole. By configuring the switch states of the frequency selective reflectors, various beam shapes can be formed and steered. Measured results of the antenna show good agreement with the calculated ones.

Wave gradiometry for USArray: Rayleigh waves

Wave gradiometry (WG) is a new array data processing technique to extract phase velocity, wave directionality, geometrical spreading, and radiation pattern from spatial gradients of waveforms. A weighted inversion method and a reducing velocity method are introduced to compute spatial gradients accurately for irregular arrays. Numerical experiments are conducted to test techniques and to evaluate the parameters determined from the WG method. We apply this method to USArray data for the western United States. In this study, Rayleigh waves from nine earthquakes with varying azimuths are analyzed. The stability of this method is shown by the similarity between the results from two nearly collocated earthquakes from the Kurile Islands. The error check shows the WG results are stable for ambient noise level as high as 10%. Phase velocities determined by WG and two station (TS) methods are statistically consistent, while these determined from beam forming method are systematically higher for wavelength larger than one quarter of the array diameter. Our results show that, first, the average phase velocities of Rayleigh waves range from 3.8 to 4.1 km/s for periods from 60 s to 150 s. This is consistent with average earth models. The prominent feature on the phase velocity map is that the Basin and Range province is dominated by velocity lows while the west coast of the United States and the north and northeastern Snake River plain are dominated by velocity highs. The Snake River plain appears to be a primary tectonic boundary. Second, azimuthal variations represent the accumulated wave directionality changes along the raypath. A velocity contrast of 0.25 km/s across the oceanic‐continental lithosphere boundary along the west coast of the United States is needed to explain the negative azimuth variations. Third, geometrical spreading is slightly anticorrelated with phase velocity, which may suggest that amplitude variations in radial directions are subject to surface wave focusing and defocusing. Fourth, similar to the wave directionality, radiation pattern variations also exhibit strong path dependence. Further theoretical and experimental studies will be conducted to understand the two amplitude parameters: geometrical spreading and radiation pattern and their relations with the local geophysical properties.

Frequency‐independent performance of elliptic profile TEM horns

AbstractThe TEM horn with elliptic E‐plane profile has been shown to give extremely wide bandwidth performance as far as VSWR and gain is concerned. In this article, the variation in radiation pattern versus frequency is explored, and it is shown that, dependant on choice, E‐plane or H‐plane radiation patterns that are virtually independent of frequency can be obtained. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 607–612, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24109

Compact Multimode Patch Antennas for MIMO Applications [Wireless Corner

This work presents the design of compact multimode patch antennas for application in medium-size MIMO terminals combining spatial and radiation-pattern diversity. This design was inspired by previous work, which proposed the use of patch antennas providing two services at two frequency bands that required different radiation patterns. These precedents are briefly reviewed, before extending the concept of the dual-pattern two-frequency case to one in which diversity is demanded at a single frequency. A design with three modes at a single frequency is also accomplished. Some prototypes have been manufactured and measured. An example of the advantages of using these multimode antennas in terms of spectral efficiency in MIMO systems is also included. The key aspect of this work is the use of short-circuited ring patch (SCRP) antennas.

Genetic algorithm optimized printed UWB sickle‐shape dipolar antenna with stable radiation pattern

AbstractA double sided sickle‐shape printed dipolar antenna optimized using genetic algorithm is proposed. The proposed antenna has a wide impedance bandwidth and small variations in radiation pattern and gain across the entire UWB frequency range. This can be used in multi‐band, OFDM and impulse radio modulation schemes, making it suitable for UWB triple mode use. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2695–2697, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22883

MEMS-Switched Parasitic-Antenna Array for Radiation Pattern Diversity

A micro-electro-mechanical series (MEMS)-switched parasitic antenna array providing radiation pattern diversity is described. A new modeling method is introduced in order to allow a fast and accurate optimization of the antenna. This method is demonstrated with the design of both passive and active prototypes at 5.6 GHz. The active prototype makes use of stand-alone packaged MEMS switches. Measured return loss and radiation patterns are in good agreement with the design, demonstrating a beam-switching at plusmn25deg

Single feed antenna with radiation pattern diversity

A vehicle diversity antenna system comprising a single-fed element together with a loaded parasitic element is described. Different termination loads on the parasitic element give rise to variations in the radiation patterns that are comparable with a four-element diversity system. There was good agreement between measured parameters and simulations.

Ray-based amplitude tomography for crosshole georadar data: a numerical assessment

Analyses of travel times and amplitudes of crosshole georadar data provide estimates of the electromagnetic velocity and attenuation of the probed media. Whereas inversions of travel times are well established and robust, ray-based inversions of amplitudes depend critically on the complex directive properties of the georadar antennae. We investigate the variations of radiation patterns in the presence of water-filled boreholes and/or changes of electrical material properties in the vicinity of the transmitters or receivers. To assess the implications of such complicating factors for ray-based georadar amplitude tomography, we generate crosshole georadar data for a suite of canonical models using a finite difference time domain (FDTD) solution of Maxwell's equations in cylindrical coordinates. The emitting dipole-type antenna is approximated by an infinitesimal vertical electric dipole, whereas a corresponding receiving antenna is emulated by recording the vertical component of the transmitted electric field. Inversions of the amplitudes of these synthetic data demonstrate that the presence of water-filled boreholes as well as changes in the material properties along the boreholes may cause substantial artifacts in the estimated attenuation structure. Furthermore, our results indicate that ray-based amplitude tomography of crosshole georadar data is unable to constrain absolute values of attenuation. Despite these inherent limitations, the method is surprisingly robust at detecting and constraining relative changes in attenuation. In particular, we find the method to be highly effective for locating conductivity contrasts that are not associated with corresponding changes in dielectric permittivity, and hence, cannot be located by travel time tomography alone.

Radiation characteristics of small slot antenna for wristwatch-type pager worn on human body

In recent years, the demand for compactness in portable radios has become increasingly stronger. This trend is more significant in pagers, and wristwatch-type pagers have been commercialized. In this article, a small slot antenna to be installed in the watchband is investigated. Since the present antenna is used in close proximity to the human body, human models for both theoretical and experimental studies are created taking into account the human body as part of the antenna structure, and the radiation characteristics of the small slot antenna actually worn on the human body are measured and calculated. It is found that a gain of about –15 dBd can be obtained even when the antenna is worn on the human body, and this is enough compared to the gain of –30 dBd required in the antenna for pagers. The radiation pattern variation due to the position change of the user is also investigated, and the radiation patterns are measured and calculated for various positions. It is found that good radiation characteristics as an antenna for pagers can be obtained even considering the arm position variation of users. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(9): 93–101, 2000

The array of two traveling-wave V-antennas as a spacecraft antenna

Variation of radiation pattern of array of two traveling-wave V-antennas and use as spacecraft antenna